1. Field of the Invention
The present invention describes a method for joining silicone-coated fabrics by using a silicone rubber adhesive.
2. Background Information
Silicone-coated fabrics have been used as electric-insulating materials, diaphragms, waterproof fabrics, sputter-preventing fabrics, belts and fire curtains. There have been recent attempts to use such fabrics as a roofing material for stadiums, gymnasiums and outdoor restaurants.
Very large-area silicone-coated fabric is difficult to produce from the standpoint of production technology. When silicone-coated fabric is to be used as a roofing substitute for buildings or as a large-scale tent material, the silicone-coated fabric manufactured at the plant, which will have a relatively small area, must then be joined because a large area is required.
Heretofore, when fabrics were to be joined, in general they were overlapped and the overlap region was sewed.
A method of making a sewn seam in which a binding tape is adhesively applied over the line of stitching to give a water tight seam is taught in U.S. Pat. No. 2,372,632, issued Mar. 27, 1945 to Webb.
A method of sealing the holes caused by sewing together sheets of coated fabric is taught in U.S. Pat. No. 2,465,374, issued Mar. 29, 1949, to Haman, et al.
A sewn seam having the elastomeric component of one section bonded to an elastomeric component of another section is taught by Woodroof in U.S. Pat. No. 4,303,712, issued Dec. 1, 1981.
Also, a method has been proposed in which the joined body is acquired by coating an adhesive on the region of the silicone-coated fabric which is to participate in joining and by overlaying the coated surface. Adhesives to be used for this purpose are, for example, silicone pressure-sensitive adhesives and condensation-curable silicone adhesives in which a crosslinking agent has been added to a silicone pressure-sensitive adhesive (U.S. application Ser. No. 513,504, filed July 13, 1983, by Blizzard and Vanwert, now abandoned and U.S. application Ser. No. 694,481, filed Jan. 22, 1985, by Blizzard and Vanwert.
Also, the moisture-curing single-package silicone adhesive used as an adhesive for silicone rubber and described in U.S. application Ser. No. 694,481, filed Jan. 23, 1985, by Blizzard and Vanwert can also be considered an adhesive for joining silicone-coated fabric.
When a silicone-coated fabric which has been joined by sewing is used as a roofing material for a building or as a large-scale tent material, the tensile stresses caused by gravity and wind pressure are concentrated around the sewing thread and failure readily occurs in this vicinity. Rain and dust then penetrate the gap in this region of the joint.
On the other hand, the silicone pressure-sensitive adhesive and the adhesive of crosslinking agent added to silicone pressure-sensitive adhesive suffer from the following problems. After coating the adhesive, the solvent must be evaporated to produce a tacky film and the bonding strength after joining is unsatisfactory.
The moisture-curing single-package silicone adhesive does not provide an adequate initial bonding strength and the joint experiences slipping or peeling during the joining operation. Also, a long time is required to cure the adhesive layer completely.
In addition, since the above-mentioned adhesives are pastes or liquids, it is difficult to coat the adhesive on the surfaces to be joined and it is difficult to obtain a uniform coat thickness.